The Lymphatic System PDF

The Lymphatic System  The Lymphatic System This topic relates to: Learning outcome(s) Describe composition and functions of lymph Identify the functions and locations of...

The Lymphatic System  The Lymphatic System This topic relates to: Learning outcome(s) Describe composition and functions of lymph Identify the functions and locations of lymphatic vessels, nodes and organs in the body Formative and summative assessment Any topic within this module could potentially have a question(s) in the exam paper Links with other topics in the module Blood, immunity Links with other modules and stages Links to stages 2 and 3 sciences Links to nursing and paramedic practice Essential knowledge for caring for people with infection, disorders of the immune system, the blood and a range of cancers 23 November 2 2024 Lymphatic system – three main functions Fluid balance About 30 litres fluid pass from blood capillaries to interstitial fluid daily; 27 litres pass back to the capillaries Excess 3 litres enter the lymphatic capillaries, this is called lymph Lymph contains – water, solutes from plasma, hormones, enzymes, waste products Lipid absorption Lipids and other substances picked up in lacteals in the small intestine, passed to lymph vessels Defence Microorganisms are filtered from the lymph by lymph nodes and the spleen Lymphocytes and macrophages destroy foreign substances The Lymphatic system Consists of: Lymph Lymph vessels Lymph nodes Lymph organs – spleen & thymus (not shown on the figure) Lymphoid tissue – tonsils Lymph capillaries, vessels and ducts Lymph capillaries Originate as blind end tubes in interstitial spaces Same structure as blood capillaries with more permeable walls Join to form lymph vessels Lymph vessels Nearly all tissues have a network of lymph vessels (not nervous system, bone, cornea, outer layers of skin) Larger vessels run along side arteries and veins Cup shaped valves ensure flow – no pump, but able to contract in rhythm Lymph ducts Eventually form lymph ducts – thoracic duct and right lymphatic duct Lymph ducts Thoracic duct Right lymphatic duct Begins at cysterna chyli – ̴1cm long, lying in neck dilated lymph channel lying Opens to right subclavian before lumbar vertebrae 1 & vein 2 Drains lymph from right side ̴40 cm long, opening to left of thorax, head & neck, right subclavian vein arm Drains lymph from legs, pelvis, abdominal cavities, left side of thorax, head & Lymph movement neck, left arm Smooth muscle contraction in walls Contraction of skeletal muscles Lymph node structure Oval or bean shaped, found in groups along length of lymph vessels Lymph passes through 8-10 nodes on way to venous circulation Outer fibrous capsule, extending into node and forming partitions – trabeculae Body contains reticular and lymphatic tissue Reticular cells form network of fibres giving internal structure to the node Lymphatic tissue contains Structure and positioning of nodes 4-5 afferent vessels carry Nodes lie throughout body, lymph to node in deep and superficial One efferent vessel taking groups Cervical nodes (neck) lymph away Axillary nodes (armpits) Concave area on each A group near mediastinum node called the hilum – an Many associated with blood artery enters and a vein vessels supplying organs, and efferent lymphatic and close to main arteries vessel leave Knee and groin nodes (inguinal nodes) Filtering and phagocytosis Lymph is filtered by reticular and lymphocytic tissues Matter filtered includes: Bacteria, dead and live phagocytes with ingested microbes, worn out and damaged tissue cells, inhaled particles Material is destroyed in lymph nodes by macrophages and antibodies produced by lymphocytes Passage of material through several nodes means materials filtered many times – cleared by time lymph enters blood circulation The spleen Largest lymph organ Lies in left hypochondriac area of abdominal cavity Similar to a large lymph node, except it contains blood instead of lymph Associated with some organs: Large intestine, stomach, diaphragm, pancreas, kidney Fibrous capsule, trabeculae The spleen Cellular material contains Entering and leaving at lymphocytes and hilum macrophages in: Splenic artery (branch of Splenic pulp coeliac vein) Red pulp suffused with blood Splenic vein (branch of portal White pulp consisting of vein) areas of lymphatic tissue Efferent lymph vessels with sleeves of lymphocytes nerves and macrophages around Note: no afferent blood vessels lymphatics entering therefore the spleen is not exposed to diseases spread in lymph Splenic functions Phagocytosis Bilirubin and iron (break down products) transported to liver (via portal and splenic veins) Storage of blood (up to 350 ml) for release when there is need in tissues e.g. in hemorrhage Immune response – spleen contains T & B lymphocytes activated in presence of antigens e.g. infection Erythropoiesis – foetal blood cell production Thymus gland In upper mediastinum, behind sternum, extending to base of neck 10-15g at birth, 30-40g at puberty, atrophies post Two lobes joined by areolar puberty tissue Associated organs: Fibrous capsule dipping into sternum, upper rib cartilage, aortic arch with body branches, brachiocephalic Lobules containing veins, trachea, lungs, branching framework of structures of neck, heart epithelial cells and Functions of thymus Lymphocytes formed in stem cells in sternum Those situated in thymus become activated T lymphocytes T lymphocytes can tell the difference between ‘self’ tissue and foreign tissue and only react to one specific antigen from millions encountered They leave the thymus and circulate in the bloodstream T-lymphocyte response to antigens declines with age Mucosa-associated lymphoid tissue (MALT) Collections of unencapsulated lymphoid tissue Contain B- and T-lymphocytes following migration from bone marrow and thymus Early detectors of invaders Do not filter lymph, so not exposed to spread of diseases via lymph In digestive and respiratory systems and urinary tract (systems exposed to outside environment) Main groups – tonsils, aggregated lymphoid follicles (Peyers patches) Summary Here we have covered: Content and function of lymph Structure of the lymphatic system Structures and functions of lymph nodes and organs Mucosa associated lymphatic tissue Reading: Chapter 14. Hole’s Essential Human Anatomy and Physiology